1. Field of the Invention
This invention relates to a wheel bearing assembly, a manufacturing method of the assembly, and a calk jig. Concretely, the invention relates to a wheel bearing assembly that is assembled by using a calking process, and a manufacturing method for the assembly as well as a calk jig for use in the manufacturing method.
2. Description of the Related Art
A wheel bearing assembly includes a wheel hub, a constant-velocity joint outer ring, and a multi-row tolling bearing in which inner ring raceway surfaces are formed on an outer peripheral surface of a wheel hub and an outer peripheral surface of a constant-velocity joint outer ring. In this type of wheel bearing assembly, the wheel hub and the constant-velocity joint outer ring are integrated by fitting a center shaft portion that is formed integrally with the constant-velocity joint outer ring into a hollow hole that is formed in a shaft center portion of the wheel hub. Furthermore, a tubular protrusion formed on a shaft end of the center shaft portion of the constant-velocity joint outer ring is calked and fixed to a calk fixation portion of an outer end surface of the wheel hub by bending it radially outward with a calk jig, and a compression in the axis direction is applied to the tubular protrusion. In this manner, the loosening between the wheel hub and the constant-velocity joint outer ring in the axis direction is substantially prevented.
With reference to FIG. 6, a method of performing a calking processing on a wheel bearing assembly 50 according to a related-art technology will be described. In FIG. 6, in the wheel bearing assembly 50, a center shaft portion 62 formed integrally with a constant-velocity joint outer ring 60 is spline-fitted to a hollow hole 54 of a wheel hub 52, and an outer race 70 of a multi-row rolling bearing is fitted onto the wheel hub 52 and the constant-velocity joint outer ring 60 integrally connected together. A guide hole 66 capable of receiving a cylindrical punch protrusion end 74 that is formed on a distal end of a calk punch 72, that is, a calk jig, is formed inside a tubular protrusion 64 that is formed on an end portion of the center shaft portion 62 of the constant-velocity joint outer ring 60. The tubular protrusion 64 is radially outwardly bent so as to be calk-fixed to a calk fixation portion 57 of an outer end surface 56 of the wheel hub 52 which is adjacent to the hollow hole 54 of the wheel hub 52, by inserting the punch protrusion end 74 of the calk punch 72 into the guide hole 66, and oscillatingly turning the calk punch 72 while pressing the calk punch 72 against the tubular protrusion 64 that is formed on an end portion of the center shaft portion 62 of the constant-velocity joint outer ring 60.
A sectional shape of a calked portion 65 that has been calk-fixed is shown in FIG. 7. In this related-art technology, the calked portion 65 formed on a distal end of the center shaft portion 62 is calk-fixed so that a distal end portion of an outer surface of the calked portion 65 is inclined toward the inner side. A calking angle β that is the angle of the inclination toward the inner side with reference to a radially outward direction from the axis of the center shaft portion 62 in a plane perpendicular to the shaft center as shown in FIG. 7 is set at about 30 degrees.
One related-art literature is Japanese Patent Application Publication No. 2001-246440 (JP-A-2001-246440) (related literature 1). The related literature 1 describes a method in which in a hub unit for a vehicle, an outer side end portion of a center shaft portion formed integrally with a constant-velocity joint outer ring is calked to an outer end surface of a wheel hub by bending the outer side end portion of the center shaft portion in radial directions from the shaft center. In addition, the related literature 1 also describes that in order to prevent deformation of the hub unit during the process of calking, restraint jigs are set on the constant-velocity joint outer ring and its center shaft portion during the calking process (see FIG. 4 in the related literature 1).
Another related-art literature is Japanese Patent Application Publication No. 2001-315502 (JP-A-2001-315502) (related literature 2). The related literature 2 describes, as a manufacturing method for a wheel hub unit for a vehicle, a method in which an end portion of a center shaft portion formed integrally with a constant-velocity joint outer ring is calked to an outer end surface of a wheel hub by bending the end portion of the center shaft portion radially outward (see FIG. 2 in the related literature 2). Although the patent literature 2 does not provide a clear description of the foregoing calking angle, it can be understood that the aforementioned calking angle is set at about 30 degrees, according to the drawings of the related literature 2. In addition, the patent literature 2 also describes that in order to prevent deformation of a hub unit for a vehicle during the process of calking, restraint jigs are set on a constant-velocity joint outer ring during the calking process (see FIG. 2 in the related literature 2).
By the way, as shown in FIG. 6, a tubular annular protrusion 58 that is protruded in the axis direction and that serves as a guide when a wheel-side member is attached is formed at a site radially outwardly of the calk fixation portion 57, on the outer end surface 56 of the wheel hub 52. Therefore, there is a concern that when the calking fixation is performed by oscillatingly turning the calk punch 72, the calk punch 72 may interfere with the annular protrusion 58 of the wheel hub 52, and therefore may deform the annular protrusion 58, depending on the calking position, the size of the calking diameter, or the magnitude of the oscillation angle of the calk punch 72.